4 panel grid tie - advice needed

[Cobs]

Hi all, i have aquired 4x Suneka 240w Solar panels, i would like to have these standing in my garden wired to a Grid Tie Inverter which i can plug into a wall socket to help get my bills down, here are the panel specs...

Max Power:240watts
OpenCircuit Voltage (VOC):36.8v
Max Power (VMP) 29.7v
Max System Voltage: 1000W

Short Circuit Current: 8.06A
Max Power Current (IMP): 8.09A
Max Series Fuse Rating: 15A

Im not sure if serial or parallel is the way to go?, ideally i would like to have all 4 panels connect into 2 cables via the MC4 Y adapters and then run 15feet to my utility room and a fuse and then to the 30/36V Grid Tie Inverter (1000w), what size fuse would i need? Would i be right in assuming a 40Amp fuse with each panel being rated at 8Amps x4 = 32A?

This is the Inverters Spec...
Rated Power 1000W
Solar Panels 60/72 cells ; 30V/36V
DC Input Range 20V-45V
MPPT Voltage 26-36VDC
AC Output 120V(90-140V) or 230V(190-260V)
Frequency 48Hz-62Hz
THD <5%
Power Factor >97.5%
Stand-by Power ＜1W
Certification CE RoHS

Many thanks for any advice

Cobs

[inetdog]

In the US there are no UL listed (approved for connection to house wiring) GTIs that are plug and cord connected.
I do not know the details of your situation in the UK, but with a 1000W inverter, at a minimum you will need to dedicate a receptacle and circuit to the inverter connection and not just use any existing receptacle.

You cannot go to a series connection for the panels since the maximum DC input of your inverter is 45V.

DC Input Range 20V-45V
MPPT Voltage 26-36VDC

The panels you have are well matched to the input requirements of the inverter as long as you connect them in parallel.
Since you have more than two panels in parallel you will need to put a fuse in series with each individual panel. The fuse size should be part of the panel specification.

Max Series Fuse Rating: 15A

[Cobs]

Ahh so i would need a 15A fuse for each panel before connecting them to the MC4 connector that makes the parallel setup ... then runs 15feet to my utility room?

I do intend to have a DC disconnect switch before the Inverter, i forgot to mention that, im also looking for an Electrical Enclosure to house the Inverter, i intend to add some digital volt and amp metres to this setup.

In UK they do allow you to feed in like this (also with a Wind Turbine) which i will be adding at some point. If im over the limit i have no issue with using Off Grid of course but where im putting these panels wont get them to max power usage due to my small garden facing West North West but every little helps i think

[lkruper]

Ahh so i would need a 15A fuse for each panel before connecting them to the MC4 connector that makes the parallel setup ... then runs 15feet to my utility room?

I do intend to have a DC disconnect switch before the Inverter, i forgot to mention that, im also looking for an Electrical Enclosure to house the Inverter, i intend to add some digital volt and amp metres to this setup.

In UK they do allow you to feed in like this (also with a Wind Turbine) which i will be adding at some point. If im over the limit i have no issue with using Off Grid of course but where im putting these panels wont get them to max power usage due to my small garden facing West North West but every little helps i think

If I understand you correctly, you putting power through a power cord with a male connector that plugs into a wall socket and the exposed male conductors will have 110v power. This is called a suicide cord and is not legal in the US. It would be dangerous in any country, but perhaps I have misunderstood what you are doing.

I purchased a manual transfer switch which is connected on the load side. I can power any circuit (it is a 10 circuit switch) independently of the grid, but it is really designed for a generator when the power goes out. Theoretically I could put solar on any circuit in my cabin while the grid powers all other circuits.

[Cobs]

Hmmm no, there are no bare / exposed wires, the setup would be ... solar panels to fuses - to dc disconnect switch - to inverter - to mains outlet (inverter comes with a dedicated 240v out lead - the same as a PC uses). Ive seen numerous people on YouTube doing it like this in the UK and USA ... like this ...

https://www.youtube.com/watch?v=S93wbGlzsJg

[lkruper]

Hmmm no, there are no bare / exposed wires, the setup would be ... solar panels to fuses - to dc disconnect switch - to inverter - to mains outlet (inverter comes with a dedicated 240v out lead - the same as a PC uses). Ive seen numerous people on YouTube doing it like this in the UK and USA ... like this ...

https://www.youtube.com/watch?v=S93wbGlzsJg

The very beginning frame shows that inverter with the two DC inputs on one side and a black cord with male plug to go into an outlet. If the DC is connected and the inverter is turned on, if you hold the cord by the business end you get a shock (don't try this at home!). That is a suicide cord.

[Cobs]

Ah yes i see what you mean by a suicide cord now, of course i wouldnt touch the pins on the plug, it would be plugged in before i allowed power to flow through it. Surprised the guy in the vid didnt mention that come to think of it but i know it would be live if the inverter was on, just hadnt heard the term "suicide cord" before. So this is illegal in the USA and UK? Seems to be a lot of people going about it or is there a safer way im not seeing? ... i guess a PC lead to a female socket would be safer, like an extension socket and i just plug things into that i want to use - making it an off-grid setup.

[lkruper]

Ah yes i see what you mean by a suicide cord now, of course i wouldnt touch the pins on the plug, it would be plugged in before i allowed power to flow through it. Surprised the guy in the vid didnt mention that come to think of it but i know it would be live if the inverter was on, just hadnt heard the term "suicide cord" before. So this is illegal in the USA and UK? Seems to be a lot of people going about it or is there a safer way im not seeing? ... i guess a PC lead to a female socket would be safer, like an extension socket and i just plug things into that i want to use - making it an off-grid setup.

We have something called the NEC (National Electrical Code) in the US and I don't know about the UK, but it seems to me you guys over there across the pond do have a measure of sophistication [perhaps you know it by the name suicide cable -> https://en.wiktionary.org/wiki/suicide_cable]

As for a safer way, it is the manual transfer switch I put in my cabin. The output of the generator or inverter terminates in a female four-prong plug. When a circuit is switched off the grid and onto the transfer switch it breaks the connection before making a new one. Mine is ten circuit and I can selectively power circuits in the cabin while leaving the others powered by the utility.

I have not looked at the device in the video, am not an electrician or an authority by any means. However from what I have read, the way house electrical lines are protected by the circuit breaker can be bypassed by putting power into an outlet with one of these bootleg (at least in the US) inverters.

If a fire started the insurance company could deny benefits.

[jflorey2]

i guess a PC lead to a female socket would be safer, like an extension socket and i just plug things into that i want to use - making it an off-grid setup.

That would make it a standalone inverter, not a grid tie one. They are very different animals.

[Mike90250]

A grid tie inverter (wire or plug-in) will not output any power, until it has qualified a good AC source (to backfeed into) for 5 minutes, and to drop power in a couple cycles if the grid fails. So there should never be any exposed voltage on the bare plug ends - IF the unit is functioning properly.
With no UL cert, it's not assured it's going to function well, most plug-ins have poor efficiency (75% vs 95%).

[inetdog]

The biggest problem (other than catching fire or other problems you might have with any non-tested appliance) is this:

If there are other receptacles (sockets) on the circuit to which you are connecting the inverter, you could add up individual loads to the circuit (each within its local fuse limit) until you have reached a load equal to the sum of the branch circuit breaker current and the current delivered by the GTI. That will be greater than the safe carrying capacity of the circuit wiring if it was done to the minimum code standard size.

The only way to be sure that this does not happen is to put the GTI on a circuit to which you connect no loads and to which nobody who is not aware of the situation can connect loads.

[Cobs]

Wow theres even more to it than it looked, thanks for all the input guys, i am not an electrician either but i always do my homework before commencing with things.

Im already considering a company installed solar installation for my roof which can hold 12 panels and would be grid tied.

These 4 panels were to experiment with / help get my bills down, so it seems i cant grid tie in in the fusebox due to it not being supported and the fusebox is on the other side of my house - indoors. Yes i know off grid is a different animal - something ive just realised wont work with this as someone already mentioned - it seeks an AC signal before it can work.

I dont think i have any circuits that dont have a load - the sockets in my utility room im guessing are a spur from the kitchens sockets which is the next room to my utility room, ill just check ... correction - the utility room sockets has their own fuse/breaker in my main fuse box, there are no loads on the sockets until the tumble dryer is turned on, this is all that runs in the utility room, its not that big a room.

So this manual transfer switch - if i bought one i can still use the setup i have? Im guessing it connects to your fusebox area or can it be conected via any socket?

[lkruper]

A grid tie inverter (wire or plug-in) will not output any power, until it has qualified a good AC source (to backfeed into) for 5 minutes, and to drop power in a couple cycles if the grid fails. So there should never be any exposed voltage on the bare plug ends - IF the unit is functioning properly.
With no UL cert, it's not assured it's going to function well, most plug-ins have poor efficiency (75% vs 95%).

That I did not know. Thanks. I also did not understand that the OP wanted to add AC to his existing circuits that were already powered (even though I understand that is how grid-tie works).

[SunEagle]

That I did not know. Thanks. I also did not understand that the OP wanted to add AC to his existing circuits that were already powered (even though I understand that is how grid-tie works).

The problem with those "quasi" grid tie plug in inverters is that even if they have the "anti-island" programming to stop working when the grid goes down there is no guarantee they will continue to work 100% of the time without having gone through a legal test procedure which is what a UL listing company performs. It only takes a single time for a failure to get someone electrocuted. So IMO those type of inverters will always have a "suicide cable" or at least a "Russian roulette" cord.

[lkruper]

So this manual transfer switch - if i bought one i can still use the setup i have? Im guessing it connects to your fusebox area or can it be conected via any socket?

I don't know if they sell them in the UK, but you can find Reliance online to see the concept. They sell both indoor and outdoor boxes. Mine was outside and mounted next to my electrical panel. The switch has ten circuits and comes pre-wired to be connected to the electrical panel. Each circuit that is selected to be used for the manual switch is spliced inside the fuse box. In my case I did not touch the 220v circuits, but that is also an option. So I can select a circuit in my transfer switch to isolate from the grid, and the rest remain on utility power. [I should add that this can be done temporarily and re-configured on the fly] I connect a generator up to the switch and power any circuit independently of the mains. The transfer connections are on the load side. It is designed to be used when the power goes out, but it does not matter one way or the other.